The first thing to do would be to try muting or unplugging your microphone to see if it is feeding back, happened to me before and took a long time to figure out the issue.

Is this only happening with MSN? Can you try another program like skype or yahoo and see if the issue still occurs? This will give an idea as to whether the problem is with the hardware or the program.

1. Update to the latest version of MSN, please post the version number here if issue persists.

2.Click Start - Run (or in vista/7 type directly into the search bar) "msconfig". Select the startup tab. Look for RTHDCPL. If it is unticked then tick it and restart the computer. If a dialog box pops up after restart select to keep the changes.

3. Update your audio drivers - this is probably not the issue as it only affects MSN but better to get it out of the way I have seen weird things over the years like a video card driver creating audio distortion in certain games.

Check if the issue is fixed after doing each of these steps, don't run them all and then check :)

These are general fixes, if none of them work let me know what microphone you're using(Built in or headset). I know the issue is audio on your side but quite often feedback from your own microphone is the cause. To test this try muting your microphone on next video conference.

Hi there, I am sorry for the delay in responding to your message. I could not find RTHDCPL in the startup tab. The audio problem has not been solved yet and I am using a built in microphone (I have got an ACER Aspire 1650 laptop). I have now a "new" problem: Live Messenger "disappears" upon signing in. I am opening a new and separate thread for this.

Hi there... I having the same problem with ACER ASPIRE 1650. Soud crackling ONLY with MSN.. I can use also toghter voip and skype and it work... if I use VOIP and MSN, the sound cracks on MSN not on VOIP.
I've tryed with one friend all three togheter and only on MSN crcks.
I've tryed the most of sugestion founded on web.
AND I'VE RE-INSTALLED WINDOWS XP, SKYPE, VOIP AND MSN, in this sequence, all NEW LAST version...
Thanks for any help.

Hi Saccon, I have also got a Aspire 1650 laptop! ... my MSN now is not working at all (opened a new and separate "discussion threat" a long time ago): everytime I sign in, the Live MSN messenger disappears from the screen. Still trying to sort it out. So, I can't check at the moment about the sound. However, sound is working perfectly with Skype.

Perhaps your ISP also has a telecoms business and does not like people "freeloading" [as he sees it] by using voice messenger services for "no" cost. But why he would throttle MSN and not Skype I do not know. Quiz them.
M$ vs Google. The battle continues.